“sqlserver”三表联如何查询“sql”语句？

假设学生表叫student,课程表叫class,选课表叫choose

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1.三层嵌套的问题

select student.name from student where student.id IN

(select choose.sid from choose where choose.cid NOT IN

(select class.id from class where class.teacher='李明'))

2.一个内连接，一个嵌套

select student.name,avg(choose.score) from

student inner join choose on student.id=choose.sid

where student.id IN

(select choose.sid from choose

where choose.score'60'

group by choose.sid

having count(choose.sid)=2)

gruop by student.id

3.一个联合查询，一个嵌套查询

select student.name from student

where student.id IN

(select c1.sid from choose c1 where choose.cid='1'

union

select c2.sid from choose c2 where choose.cid='2'

on c1.sid=c2.sid

)

4.其实就是自连接查询和行列交换的问题：

select student.id,

(case choose.id when '1' then choose.score end) as 1号课成绩,

(case choose.id when '2' then choose.score end) as 2号课成绩,

from student inner join choose on student.id=choose.sid sc1,

student inner join choose on student.id=choose.sid sc2

where sc1.id='1'

and sc2.id='2'

and sc1.scoresc2.score

sqlserver的查询语句和插入更新语句怎么用

sqlserver的查询语句和插入更新语句怎么用

1、说明：复制表(只复制结构,源表名：a 新表名：b)

select * into b from a where 11（仅用于SQlServer）

2、说明：拷贝表(拷贝数据,源表名：a 目标表名：b)

insert into b(a, b, c) select d,e,f from a

sqlserver怎样写查询语句完成下面的运算

将两条查询语句作为子查询的一部分连表.

select t1.count1+t2.count2 as 'countSum',t1.branch

(select count as count1, branch from table1 group by branch)t1

(select count as count2, branch from table2 group by branch)t2 on t1.branch =t2.branch

这种写法有一个潜在的限制,t1中的branch 必须包含t2,所以你的需求一般这么写:

select sum(counts)counts,branch

from(select * from(select count as counts, branch from table1 group by branch)t1

union

select * from(select count as counts, branch from table2 group by branch )t1)t

group by branch

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